21 patients with polytetrafluoroethylene grafts inserted for hemodialysis access were studied to assess the hemodynamic parameters. Mean graft flow was 1.9 l/min with a range of 0.2-3.8 l/min. Intragraft pressure varied from 1 to 83 mmHg and was dependent on systemic pressure, graft flow and the presence of stenotic lesions. Mean cardiac output was 7.1 l/min and index 4.0 l/min and was positively correlated with graft flow. By obtaining this data surgical corrective action was taken in several patients prospectively thus removing the abnormalities and ensuring continued graft patency. The techniques described are reproducible and simple and can be carried out in less than five minutes with minimal patient discomfort or hazard.